1. Field of the Invention
The invention relates to furnances for smelting and refining metals and more particularly relates to blast furnaces for smelting lead ores and lead bearing residues.
2. Brief Description of the Prior Art
Prior hereto, blast furnaces have included tuyeres for distribution of oxygen and oxygen containing gases such as air to the furnace smelting zone. During the course of furnace operation, the tuyeres generally become slagged over (blocked) at least partially. Other conditions existing in the tuyeres and/or conduits delivering oxygen to the tuyeres may reduce the flow rates of oxygen to certain tuyeres while not affecting other tuyeres. This imbalance of air/oxygen flow to different zones of the lead crucible may result in irregular smelting of the ore compositions, with consequent uneven charge descent. So called "blow holes" are created in a furnace charge when an unusually high volume of air/oxygen passes through a concentrated area of charge, blowing excessive amounts of charge out of the furnace. In addition, uneven distribution of air/oxygen over the smelting zone results in an unpredicatable and uncontrollable location of said zone (a factor in creating blow holes and slagging the tuyeres), resulting in loss of slag composition control, excessive volatilization of lead and partially smelted accretions building up on the shaft of the vertical blast furnace. These problems in the prior art furnaces are well documented; see for example Metallurgy of Lead and Zinc, AIME, 121, (1936), pgs. 65, 98 and 105. Corrective measures generally require shut-down of the furnace to remove slag, accretion build-up etc. It is appreciated by those skilled in the art that such shut-downs are costly in terms of lost production time, efficiency of the overall smelting operation and maintenance costs.
The improved lead blast furnace of the present invention obviates the above described problems associated with the prior art furnaces, thereby increasing the tonnage of lead bullion produced by 10 to 15 percent over prior art furnaces of comparable capacity.